The Korean War was a military conflict between North Korea and South Korea (Republic of Korea), backed by the US-led United Nations forces, from June 1950 to July 1953, in the Korean peninsula. The war began on June 25, 1950, (Sunday), when the communist forces of North Korea crossed the 38th parallel, initiating the invasion of South Korea in a military operation called "Operation Pokpoong" (Storm). By August 4, 1950, the communist forces had occupied almost 85 % of South Korea, except for a small enclave in the south called "Pusan Perimeter". Nevertheless, the final offensive of Operation Pokpoong was held off by American and South Korean forces in the southern tip of the peninsula.
In order to liberate South Korea, the American commander, General Douglas MacArthur, began the United Nation counter-offensive, landing at Inchon, on the northwestern coast of South Korea (near the 38th parallel), on September 15, 1950. This invasion force was composed of US Marine Corps units and British and South Korean elements. In the following weeks and months, the UN forces kept their drive north, crossing the 38th Parallel towards Yalu River, in direction of the Chinese border as they pushed back both North Korean and Chinese troops, which had been sent by Mao Tse-tung in late October. MacArthur wanted to push all the way into China, defeating this nation to finally unify Korea into a free democratic country, but he was forced to resign by President Harry Truman (Democrat). Thus, the war got bogged down in a stalemate, with the front line extending in a jagged pattern from west to east about 10 miles north of the 38th parallel; many battles were ferociously fought as the forces of both sides moved back and forth, conquering and losing the hill-strewn terrain.
Finally, after two years of negotiations, on July 27, 1953, the United Nations Command, North Korea, and the Chinese commanders signed the armistice agreement, that put an end to the Korean War. But military tension between North Korea and South Korea still exists since this armistice was not a peace treaty but truce.